Temporary wet strength resin for paper applications

ABSTRACT

A thermosetting resin comprising a reacted A) first partially crosslinked glyoxalated polymer comprising a reacted (i) first polyacrylamide backbone and (ii) a first glyoxal component; and B) a second crosslinked glyoxalated polymer comprising a reacted (i) second polyacrylamide backbone and (ii) a second glyoxyal component; such that the first polyacrylamide backbone has a molecular weight that is less than the molecular weight of the second polyacrylamide backbone; and the first polyacrylamide backbone and the second polyacrylamide backbone have a weight ratio ranging from 75:25 to 95:5. Methods for making and using the resin. Fibrous substrates made with the resin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims priority to U.S. patentapplication Ser. No. 12/509,762 filed Jul. 27, 2009, which is a divisionof U.S. patent application Ser. No. 11/241,565 filed Sep. 30, 2005 andissued as U.S. Pat. No. 7,608,665 on Oct. 27, 2009, the disclosures ofwhich are incorporated herein by reference.

BACKGROUND

The industry has had a long felt need for a thermosetting resin that iscapable of imparting a highly useful combination of high dry tensilestrength and high temporary wet strength to a paper product.

U.S. Pat. No. 3,556,932, for instance, discloses a composition thatimparts high dry tensile strength to paper. Unfortunately, it has beendiscovered that the resin loses approximately only 50% of its wettensile when soaked in water for 30 minutes. Paper manufacturers andconsumers would prefer to have a resin that loses more during such aperiod of time. U.S. Pat. No. 4,605,702 discloses a composition thatimparts high temporary wet strength properties to paper such that 60 to80% of the wet tensile is lost when soaked in water for 30 minutes.

It would be highly useful to develop a resin, which when applied topaper, has a temporary wet tensile properties of the same order ofmagnitude as U.S. Pat. No. 4,605,702 but a dry tensile strengthintermediate to both U.S. Pat. No. 3,556,932 and U.S. Pat. No.4,605,702.

For the foregoing reasons, there is a need to develop an improvedthermosetting strength resin.

SUMMARY

The invention relates to a thermosetting resin comprising a reacted A)first partially crosslinked glyoxalated polymer comprising a reacted (i)first polyacrylamide backbone and (ii) a first glyoxal component; and B)a second crosslinked glyoxalated polymer comprising a reacted (i) secondpolyacrylamide backbone and (ii) a second glyoxyal component. The firstpolyacrylamide backbone has a molecular weight that is less than themolecular weight of the second polyacrylamide backbone, and the firstpolyacrylamide backbone and the second polyacrylamide backbone have aweight ratio ranging from 75:25 to 95:5.

In one embodiment, the invention relates to a method for making athermosetting resin including the steps of: (a) treating a firstpolyacrylamide backbone with a first glyoxal component, glyoxalating thefirst polyacrylamide backbone, and thereby forming a first partiallycrosslinked polyacrylamide backbone; (b) adding a second polyacrylamidebackbone and a second glyoxal component to the first partiallycrosslinked backbone, thereby glyoxalating the first partiallycrosslinked polyacrylamide backbone and the second crosslinkedpolyacrylamide backbone in situ and forming the thermosetting resin,such that the first polyacrylamide backbone has a lower molecular weightthan the molecular weight of the second polyacrylamide backbone; and thefirst polyacrylamide backbone and the second polyacrylamide backbonehave a weight ratio ranging from 75:25 to 95:5.

In another embodiment, the invention relates to a method for makingpaper comprising treating a fibrous substrate with a thermosettingresin, and forming the paper, wherein the resin comprises reacted:

A) first partially crosslinked glyoxalated polymer comprising a reacted(i) first polyacrylamide backbone and (ii) a first glyoxal component;and

B) a second crosslinked glyoxalated polymer comprising a reacted (i)second polyacrylamide backbone and (ii) a second glyoxyal component;

wherein the first polyacrylamide backbone has a molecular weight that isless than the molecular weight of the second polyacrylamide backbone;and

wherein the first polyacrylamide backbone and the second polyacrylamidebackbone have a weight ratio ranging from 75:25 to 95:5.

In another embodiment, the invention relates to a paper product that isthe reaction product of a fibrous substrate and a thermosetting resincomprising a reacted A) first partially crosslinked glyoxalated polymercomprising a reacted (i) first polyacrylamide backbone and (ii) a firstglyoxal component; and B) a second crosslinked glyoxalated polymercomprising a reacted (i) second polyacrylamide backbone and (ii) asecond glyoxyal component, such that the first polyacrylamide backbonehas a molecular weight that is less than the molecular weight of thesecond polyacrylamide backbone, and the first polyacrylamide backboneand the second polyacrylamide backbone have a weight ratio ranging from75:25 to 95:5.

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims.

DESCRIPTION

The invention is based on the discovery that under carefully controlledconditions, it is possible to make a thermosetting resin that imparts ahighly useful combination of high dry tensile strength and hightemporary wet strength to a paper product under certain conditions.

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, and the like, used in the specification and claims are to beunderstood as modified in all instances by the term “about.” Variousnumerical ranges are disclosed in this patent application. Because theseranges are continuous, they include every value between the minimum andmaximum values. Unless expressly indicated otherwise, the variousnumerical ranges specified in this application are approximations.

The thermosetting resin of the invention includes a reacted A) firstpartially crosslinked glyoxalated polymer comprising a reacted (i) firstpolyacrylamide backbone and (ii) a first glyoxal component; and B) asecond crosslinked glyoxalated polymer comprising a reacted (i) secondpolyacrylamide backbone and (ii) a second glyoxyal component. The firstpolyacrylamide backbone has a molecular weight that is less than themolecular weight of the second polyacrylamide backbone, and the firstpolyacrylamide backbone and the second polyacrylamide backbone have aweight ratio ranging from 75:25 to 95:5.

The first polyacrylamide backbone is a vinyl addition polymer that isselected from the group consisting of (meth)acrylamide, vinyl acetate,styrene, methyl (meth)acrylate, (meth)acrylic acid, vinyl alcohol,diallyldimethylammonium chloride, diallyldimethylammonium sulfate, vinylpyrrolidone, (meth) acrylonitrile, dimethylaminoethyl (meth)acrylate,dimethylaminoethyl (meth)acrylate quaternaries, diethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate quaternaries,N-methylol acrylamide, manniched acrylamide quaternaries, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate,(meth)acrylamidopropyltrimethylammonium chloride, succinic acid,itaconic acid, maleic acid, alkylcarboxyvinyl amine, and combinationsthereof.

The first polyacrylamide backbone and the second polyacrylamide backbonegenerally have a weight ratio ranging from 75:25 to 95:5. In oneembodiment, the first polyacrylamide backbone and the secondpolyacrylamide backbone have a weight ratio ranging from 80:20 to 90:10.The first backbone has a weight average molecular weight ranging from500 to 5000 daltons. In one particularly useful embodiment, the firstbackbone has a weight average molecular weight 2000 daltons. In oneembodiment, the first partially crosslinked glyoxalated polyacrylamidebackbone has a cationic charge.

The second polyacrylamide backbone is a vinyl addition polymer selectedfrom the group consisting of (meth)acrylamide, vinyl acetate, styrene,methyl (meth)acrylate, (meth)acrylic acid, vinyl alcohol,diallyldimethylammonium chloride, diallyldimethylammonium sulfate, vinylpyrrolidone, (meth)acrylonitrile, dimethylaminoethyl (meth)acrylate,dimethylaminoethyl (meth)acrylate quaternaries, diethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate quaternaries,N-methylol acrylamide, manniched acrylamide quaternaries, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate,(meth)acrylamido-propyltrimethylammonium chloride, succinic acid,itaconic acid, maleic acid, alkylcarboxyvinyl amine, and combinationsthereof.

The second backbone has a weight average molecular weight ranging from6000 to 25,000 daltons. In one particularly useful embodiment, thesecond backbone has a weight average molecular weight 12,000 daltons.

The charge of the first or second polyacrylamide backbones can vary,depending on the application and the product specifications that arerequired in a given situation.

In one embodiment, when the resin is nonionic or ionic, the firstpartially crosslinked glyoxalated polyacrylamide backbone or the secondpolyacrylamide backbone further includes a non-ionic or anioniccomponent selected from the group consisting of acrylamide, acrylicacid, methacrylic acid, succinic acid, itaconic acid, andmethacrylamide.

In another embodiment, when the resin is nonionic or ionic, the resinfurther comprises (i) a first partially crosslinked glyoxalatedpolyacrylamide backbone or (ii) the second polyacrylamide backbonefurther comprises non-ionic component selected from the group consistingof styrene copolymers, acrylate ester, methacrylate ester, vinylacetate, and combinations thereof. In one embodiment, the firstpolyacrylamide backbone has a cationic charge. In another embodiment,the second polyacrylamide backbone has a cationic charge.

Advantageously, the invention also provides a method for making athermosetting resin that involves the steps of (a) treating a firstpolyacrylamide backbone with a first glyoxal component, glyoxalating thefirst polyacrylamide backbone; and thereby forming a first partiallycrosslinked polyacrylamide backbone; (b) adding a second polyacrylamidebackbone and a second glyoxal component to the first partiallycrosslinked backbone, thereby glyoxalating the first partiallycrosslinked polyacrylamide backbone and the second crosslinkedpolyacrylamide backbone in situ and forming the thermosetting resin,such that the first polyacrylamide backbone has a lower molecular weightthan the molecular weight of the second polyacrylamide backbone; and thefirst polyacrylamide backbone and the second polyacrylamide backbonehave a weight ratio ranging from 75:25 to 95:5.

The conditions at which the resin is made can vary, depending on factorssuch as available equipment, specific needs, and the like. Theglyoxalation pH of the first and second stages in steps (a) and (b),ranges from 7 to 9. In one embodiment, the pH is from 7.5 to 8.5. Inanother embodiment, the pH ranges from 7.9 to 8.3.

The method is carried out at a temperature ranging from 15 to 35° C. Inanother embodiment, the temperature ranges from 25 to 32° C., or from 27to 30° C. The simultaneous glyoxalation of the first polyacrylamidebackbone and the second polyacrylamide backbone can continue until thesolution has a viscosity that is sufficient to make a resin with theproperties of this invention. Generally, the simultaneous glyoxalationof the first polyacrylamide backbone and the second polyacrylamidebackbone continues until the solution has a #3 Shell Cup viscosity of 27seconds.

The first partially crosslinked backbone solution has a viscosity thatvaries, depending on the application. In one embodiment, the firstpartially crosslinked backbone solution has a #3 Shell Cup viscosity of9 seconds.

The solids content of the first partially crosslinked backbone solutionvaries depending on the application. In one embodiment, the firstpartially crosslinked backbone solution has a solids content rangingfrom 17 to 22%. In another embodiment, the first partially crosslinkedbackbone solution has a solids content ranging from 18 to 20%. Thesolids content of the final resin that is produced generally is at least17% and can range from 17% to 24%.

In one embodiment, the method further includes the step of glyoxalatingthe first polyacrylamide backbone and the second polyacrylamide backbonesimultaneously, under conditions that cause the formation of thethermosetting resin.

In one embodiment, the resin composition is added to a dilute aqueoussuspension of paper pulp and the pulp is formed into a fiber mat, anddried in a known manner. The fibrous substrate treated with the strengthcomposition can be any substrate of a paper product, which when treatedwith the strength composition made in accordance to the invention,acquires strength properties that are suitable for its intended use. Inone embodiment, the fibrous substrate of the invention can include anyfibrous substrate of a pulp slurry used to make paper products.Generally, the invention can be used in slurries forming dry board, finepaper, towel, tissue and newsprint products. Dry board applicationsinclude liner, corrugated medium and bleached.

The paper product made from the fibrous substrate may include paper orboard, bleached or unbleached that is treated on the surface in a sizepress or by spraying with a sizing composition of the invention.

In use, the invention advantageously provides a method for making paperthat includes the steps treating a fibrous substrate with athermosetting resin containing the reacted a thermosetting resincomprising a reacted A) first partially crosslinked glyoxalated polymercomprising a reacted (i) first polyacrylamide backbone and (ii) a firstglyoxal component; and B) a second crosslinked glyoxalated polymercomprising a reacted (i) second polyacrylamide backbone and (ii) asecond glyoxyal component;

where the first polyacrylamide backbone has a molecular weight that isless than the molecular weight of the second polyacrylamide backbone;and the first polyacrylamide backbone and the second polyacrylamidebackbone have a weight ratio ranging from 75:25 to 95:5.

The resin made in accordance to the invention can be applied by avariety of ways. In one embodiment, for instance, the resin compositionis added at the size press. Alternatively, the resin composition can beadded at a water box. Also, the resin composition is applied using aspraying application. The method is a versatile system that allowspapermakers to work under various conditions, depending on theirrespective needs. The method of the invention allows papermakers to nowmake paper which requires the particular combination of high dry tensilestrength and high temporary wet strength to a paper product.

In one embodiment, the invention also includes a paper productcontaining the reaction product of a thermosetting resin comprising areacted A) first partially crosslinked glyoxalated polymer comprising areacted (i) first polyacrylamide backbone and (ii) a first glyoxalcomponent; and B) a second crosslinked glyoxalated polymer comprising areacted (i) second polyacrylamide backbone and (ii) a second glyoxyalcomponent; where the first polyacrylamide backbone has a molecularweight that is less than the molecular weight of the secondpolyacrylamide backbone; and the first polyacrylamide backbone and thesecond polyacrylamide backbone have a weight ratio ranging from 75:25 to95:5 and (C) a fibrous substrate component. The finished product caninclude paperboard, fine paper, newsprint, other wood-containing papergrades, and combinations thereof.

The resin imparts useful properties to fibrous substrates. For instance,when the resin treats a tissue fibrous substrate, the tissue fibroussubstrate exhibits a thirty minute temporary wet strength decay rangingfrom 60% to 80%. The resin of the invention, when used in accordance tothe invention, produces fibrous substrates having a temporary wettensile properties of the same order of magnitude as U.S. Pat. No.4,605,702 but a dry tensile strength intermediate to both U.S. Pat. No.3,556,932 and U.S. Pat. No. 4,605,702.

The invention is further described in the following illustrativeexamples in which all parts and percentages are by weight unlessotherwise indicated.

EXAMPLES Example 1

The first backbone, component A, was prepared according to U.S. Pat. No.4,605,702. The second backbone, component 8, was prepared according toU.S. Pat. No. 3,556,932. A glass vessel equipped with a magneticstirring bar, pH meter probe and thermometer was charged with 178.01parts of 25.28% component A, 47.7 parts of water, and 36.88 parts of 40%glyoxal. The solution was maintained at 30° C. by means of a heatingbath during the course of the method. While stirring, the pH of thesolution was adjusted to 8.3 with 9 parts of 10% sodium hydroxide. Totalorganic solids in the solution was 22%. The reaction was maintained atpH 8.3. Progress of the reaction was monitored by means of a #3 Shellcup. When viscosity has advanced to 9 seconds, a second charge to thevessel is made. This charge was comprised of 25.57 parts of 44%component B, 9.22 parts of 40% glyoxal, and 107.04 parts of water. ThepH was adjusted to 8.3 with 1.5 parts of 10% sodium hydroxide. Again, apH of 8.3 was maintained by periodic addition of 10% sodium hydroxide.Temperature was also maintained at 30° C. When a viscosity of 22 secondswas achieved, the pH was decreased to 7.8 with 10% sulfuric acid. When aviscosity of 27 seconds was achieved, the reaction was quenched byadjusting the pH of the polymer solution to 3.2. Total reaction time is5.25 hr.

Example 2

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 184.96 parts of 24.33% component A, 40.3parts of water and 36.88 parts of 40% glyoxal. The solution wasmaintained at 30° C. by means of a heating bath during the course of themethod. While stirring, the pH of the solution was adjusted to 8.3 with9.45 parts of 10% sodium hydroxide. Total organic solids in the solutionwas 22%. The reaction was maintained at pH 8.3. The progress of thereaction was monitored by means of a #3 Shell cup. When the viscosityhas advanced to 9 seconds, a second charge to the vessel is made. Thischarge contained 11.36 parts of 44% component B, 4.1 parts of 40%glyoxal, and 80.82 parts of water. The pH was adjusted to 8.3 with 0.96parts of 10% sodium hydroxide. The temperature was also maintained at30° C. After addition of the second charge, the ratio between componentsA and B on a real weight basis was 90 to 10 and total organic solids inthe solution was 18%. When a viscosity of 22 seconds was achieved, thepH was decreased to 7.5 with 10% sulfuric acid. When a viscosity of 27seconds was achieved, the reaction was quenched by adjusting the pH ofthe polymer solution to 3.3. The total reaction time was 6 hr 35 min.

To an aqueous pulp at 0.6% consistency and pH 5.5 composed of 1:1softwood:hardwood fibers beaten to a CSF of 486 ml was added sufficientquantity of the glyoxalated copolymer of Example 1 to provide a dose of5 kilograms of resin per ton of dry pulp. The pulp pH was adjusted to5.5 and the mixture was then stirred briefly to permit absorption of the15 resin onto the fiber. From this mixture was then produced severaltwenty centimeters by twenty centimeters, 74 grams per square meterbasis weight hand sheets using a stationary deckle Noble and Woodpapermaking machine. The web was pressed between blotters and dried on arotary drum drier at a temperature of 116° C. Tensile testing of paperthus formed was accomplished according to TAPPI Test Methods # T 456, UM453. The results are set forth in Table 1, below. The % Decay wasdetermined by soaking the treated paper in water (as described in U.S.Pat. No. 4,603,176) for 30 minutes.

TABLE 1 Tensile Tensile Tensile Strength Strength Strength 30 minuteDose (dry) Wet soak Resin (kg/ton) (kN/m) (kN/m) (kN/m) % Decay Example1 5 3.23 0.45 0.16 63.7 Example 2 5 3.89 0.47 0.12 67.9 U.S. Pat. No. 53.08 0.39 0.14 64.1 4,605,702 (Comparative) U.S. Pat. No. 5 3.74 0.490.28 41.9 3,556,932 (Comparative

These experiments show the 80/20 and 90/10 ratios of backbones preparedaccording to the preferred method. The table contains comparative datafor PAREZ® 631 NC Wet Strength Resin (U.S. Pat. No. 3,556,932) andPAREZ®745 Wet Strength Resin (U.S. Pat. No. 4,605,702).

Example 3

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 184.96 parts of 24.33% component A, 40.3parts of water and 36.88 parts of 40% glyoxal. The solution wasmaintained at 30° C. by means of a heating bath during the course of themethod. While stirring, the pH of the solution was adjusted to 8.3 with9.32 parts of 10% sodium hydroxide. Total organic solids in the solutionwere 22%. The reaction was maintained at pH 8.3. Progress of thereaction was monitored by means of a #3 Shell cup. When the viscosityhad advanced to 9 seconds, a second charge to the vessel was made. Thischarge was composed of 43.83 parts of 44% component B, 15.8 parts of 40%glyoxal and 139.65 parts of water. The pH was adjusted to 8.3 with 3.13parts of 10% sodium hydroxide. Temperature was also maintained at 30° C.After addition of the second charge, the ratio between components A andB on a real weight basis is 70 to 30 and total organic solids in thesolution was 18%. When a viscosity of 22 seconds was achieved, the pHwas decreased to 7.5 with 10% sulfuric acid. When a viscosity of 27seconds was achieved, the reaction was quenched by adjusting the pH ofthe polymer solution to 3.3. Total reaction time was 4 hr 55 min. Theresults are shown in Table 2 below.

TABLE 2 Tensile Tensile Tensile Strength Strength Strength 30 minuteDose (dry) Wet soak Resin (kg/ton) (kN/m) (kN/m) (kN/m) % Decay Example3 5 3.55 0.30 0.20 31.98 U.S. Pat. No. 5 3.75 0.48 0.28 41.76 3,556,932Comparative

This experiment shows that a 70/30 ratio of backbones prepared accordingto the preferred method provides a resin with essentially equivalentperformance to PAREZ 631 NC, and therefore does not possess therequisite temporary wet strength.

Comparative Example 4

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 69.41 parts of 26.18% component A, 4.57parts of 44.15% component B, 26.21 parts of water and 16.55 parts of 40%glyoxal. The ratio between components A and B on a real weight basis was90 to 10 solution was maintained at 30° C. by means of a heating bathduring the course of the method. While stirring, the pH of the solutionwas adjusted to 8.3 with 4.08 parts of 10% sodium hydroxide. Totalorganic solids in the solution was 22.19%. The reaction was maintainedat pH 8.3. Progress of the reaction was monitored by means of a #3 Shellcup. When a viscosity of 22 seconds was achieved, the pH was decreasedto 7.5 with 10% sulfuric acid. When viscosity of 27 seconds wasachieved, the reaction was quenched by adjusting the pH of the polymersolution to 3.3. Total reaction time was 3 hr 20 min.

Comparative Example 5

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 61.69 parts of 26.18% component A, 9.15parts of 44.15% component B, 29.43 parts of water, and 16.55 parts of40% glyoxal. The ratio between components A and B on a real weight basiswas 80 to 20. The solution was maintained at 30° C. by means of aheating bath during the course of the method. While stirring, the pH ofthe solution was adjusted to 8.3 with 4.0 parts of 10% sodium hydroxide.Total organic solids in the solution was 22.19%. The reaction wasmaintained at pH 8.3. Progress of the reaction was monitored by means ofa #3 Shell cup. When viscosity of 22 seconds was achieved, the pH wasdecreased to 7.5 with 10% sulfuric acid. When viscosity of 27 secondswas achieved, the reaction was quenched by adjusting the pH of thepolymer solution to 3.3. Total reaction time was 1 hr 45 min.

Comparative Example 6

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 53.98 parts of 26.18% component A, 13.72parts of 44.15% component B, 32.54 parts of water, and 16.55 parts of40% glyoxal. The ratio between components A and B on a real weight basiswas 70 to 30. The solution was maintained at 30° C. by means of aheating bath during the course of the method. While stirring, the pH ofthe solution was adjusted to 8.3 with 4.03 parts of 10% sodiumhydroxide. Total organic solids in the solution was 22.19%. The reactionwas maintained at pH 8.3. Progress of the reaction was monitored bymeans of a #3 Shell cup. When a viscosity of 22 seconds was achieved,the pH was decreased to 7.5 with 10% sulfuric acid. When a viscosity of27 seconds was achieved, the reaction was quenched by adjusting the pHof the polymer solution to 3.3. Total reaction time was 1 hr 25 min.

Comparative Example 7

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 46.27 parts of 26.18% component A, 18.28parts of 44.15% component B, 36.01 parts of water, and 16.55 parts of40% glyoxal. The ratio between components A and B on a real weight basiswas 60 to 40. The solution was maintained at 30° C. by means of aheating bath during the course of the method. While stirring, the pH ofthe solution was adjusted to 8.3 with 3.7 parts of 10% sodium hydroxide.Total organic solids in the solution was 22.19%. The reaction wasmaintained at pH 8.3. Progress of the reaction was monitored by means ofa #3 Shell cup. When viscosity of 22 seconds was achieved, the pH wasdecreased to 7.5 with 10% sulfuric acid. When a viscosity of 27 secondswas achieved, the reaction was quenched by adjusting the pH of thepolymer solution to 3.3. Total reaction time was 1 hr 30 min. Theresults are shown in Table 3 below.

TABLE 3 Tensile Strength 30 Min Dose Dry Wet Soak % Resin Ratio(kg//ton) (kN/m) (kN/m) (kN/m) Decay Comparative 90:10 5 3.46 0.40 0.2050.88 Example 4 Comparative 80:20 5 3.38 0.35 0.18 48.76 Example 5Comparative 70:30 5 3.24 0.33 0.17 47.34 Example 6 Comparative 60:40 53.42 0.34 0.20 41.24 Example 7 Comparative 5 3.48 0.43 0.18 58.90Example U.S. Pat. No. 4,605,702 Comparative 5 3.73 0.56 0.31 44.79Example U.S. Pat. No. 3,556,932

These experiments demonstrate the resins prepared by blending bothbackbones together prior to glyoxalation. In order, they are the 90/10,80/20, 70/30 and 60/40 backbones which are subsequently glyoxalatedunder standard conditions. Only the 90/10 example (Example 4)demonstrates results which are close to the PAREZ 745 resin control.However, it also demonstrates that the % decay was not as good as thatin PAREZ 745 resin. Each of these blend shows dry strength propertieswhich are not superior to the PAREZ 745 resin control and the % decaydiminishes as the amount of the higher molecular weight backbone wasincreased.

Comparative Example 8

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 133.7 parts of 24.33% component A, 18.48parts of 44% component B, 106.99 parts of water, and 33.35 parts of 40%glyoxal. The ratio between components A and B on a real weight basis was80 to 20. The solution was maintained at 30° C. by means of a heatingbath during the course of the method. While stirring, the pH of thesolution was adjusted to 8.3 with 7.5 parts of 10% sodium hydroxide.Total organic solids in the solution was 18%. The reaction wasmaintained at pH 8.3. Progress of the reaction was monitored by means ofa #3 Shell cup. When a viscosity of 21 seconds was achieved, the pH wasdecreased to 7.8 with 10% sulfuric acid. When a viscosity of 27 secondswas achieved, the reaction was quenched by adjusting the pH of thepolymer solution to 3.3. Total reaction time was 3 hr 13 min

Example 9

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 167.12 parts of 24.33% component A, 61.27parts of water and 33.35 parts of 40% glyoxal. The solution wasmaintained at 30° C. by means of a heating bath during the course of themethod. While stirring, the pH of the solution was adjusted to 8.3 with8.26 parts of 10% sodium hydroxide. Total organic solids in the solutionwas 20%. The reaction was maintained at pH 8.3. Progress of the reactionwas monitored by means of a #3 Shell cup. When viscosity has advanced to9 seconds, a second charge to the vessel was made. This charge wascomprised of 23.11 parts of 44% component B, 8.34 parts of 40% glyoxal,and 34.75 parts of water. The pH was adjusted to 8.3 with 1.3 parts of10% sodium hydroxide. Temperature was also maintained at 30° C. Afteraddition of the second charge, the ratio between components A and B on areal weight basis was 80 to 20 and total organic solids in the solutionwas 20%. When a viscosity of 21 seconds was achieved, the pH wasdecreased to 7.9 with 10% sulfuric acid. When a viscosity of 30 secondswas achieved, the reaction was quenched by adjusting the pH of thepolymer solution to 3.3. Total reaction time was 4 hr 10 min.

Comparative Example 10

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 20.55 parts of 44% component B, 70.95 partsof water, and 7.4 parts of 40% glyoxal. The solution was maintained at30° C. by means of a heating bath during the course of the method. Whilestirring, the pH of the solution was adjusted to 8.3 with 1.1 parts of10% sodium hydroxide. Total organic solids in the solution was 12%. Thereaction was maintained at pH 8.3. Progress of the reaction wasmonitored by means of a #3 Shell cup. When viscosity has advanced to 8seconds, a second charge to the vessel was made. This charge wascomprised of 148.62 parts of 24.33% component A and 29.64 parts of 40%glyoxal. The pH was adjusted to 8.3 with 6.4 parts of 10% sodiumhydroxide. Temperature was also maintained at 30° C. After addition ofthe second charge, the ratio between components A and B on a real weightbasis was 80 to 20 and total organic solids in the solution was 21.08%.When a viscosity of 22 seconds was achieved, the pH was decreased to 7.5with 10% sulfuric acid. When a viscosity of 27 was achieved, thereaction was quenched by adjusting the pH of the polymer solution to3.3. Total reaction time was 3 hr 30 min. The results are shown in Table4 below.

TABLE 4 Tensile Tensile Tensile Strength Strength Strength 30 minuteDose Dry Wet soak Resin (kg/ton) (kN/m) (kN/m) (kN/m) % Decay Example 85 3.26 0.47 0.23 52.03 Comparative Example 9 5 3.28 0.51 0.08 83.51Example 10 5 3.14 0.41 0.22 45.73 Comparative U.S. Pat. No. 5 2.96 0.420.16 64.2 4,605,702 Comparative U.S. Pat. No. 5 3.54 0.53 0.34 37.053,556,932 Comparative

As shown above in Table 4, Example 8 shows that an 80/20 blend ofbackbones when glyoxalated at 18% solids gives improved dry tensile overPAREZ 745 but does not provide as good wet tensile decay. Example 9shows that an 80/20 blend of backbones prepared according to thisinvention with the solids in the middle of the claimed ranged and withthe second backbone being added after a development of viscosity of 9sec provides a resin with acceptable dry tensile strength and withacceptable wet tensile decay. Example 10 illustrates the effect ofreversing the addition of the backbones in the invention method. Thehigher molecular weight backbone was glyoxalated first and the lowermolecular weight backbone was glyoxalated second. Although good drytensile strength was observed, the % wet tensile decay was notacceptable.

Example 11

A vessel equipped with a magnetic stiffing bar, pH meter probe andthermometer was charged with 66.38 parts of 24.33% component A, 13.61parts of water, and 13.24 parts of 40% glyoxal. The solution wasmaintained at 30° C. by means of a heating bath during the course of themethod. While stirring, the pH of the solution was adjusted to 8.3 with3.39 parts of 10% sodium hydroxide. Total organic solids in the solutionwas 22.2%. The reaction was maintained at pH 8.3. Progress of thereaction was monitored by means of a #3 Shell cup. When viscosity hasadvanced to 9 seconds, a second charge to the vessel was made. Thischarge was comprised of 9.18 parts of 44% component B, 3.31 parts of 40%glyoxal, and 10.83 parts of water. The pH was adjusted to 8.3 with 0.61parts of 10% sodium hydroxide. Temperature was also maintained at 30° C.After addition of the second charge, the ratio between components A andB on a real weight basis was 80 to 20 and total organic solids in thesolution was 22.2%. When a viscosity of 22 seconds was achieved, the pHwas decreased to 7.9 with 10% sulfuric acid. When a viscosity of 27seconds was achieved, the reaction was quenched by adjusting the pH ofthe polymer solution to 3.3. Total reaction time was 3 hr 16 min.

Example 12

A vessel equipped with a magnetic stirring bar, pH meter probe andthermometer was charged with 66.38 parts of 24.33% component A, 13.61 5parts of water, and 13.24 parts of 40% glyoxal. The solution wasmaintained at 30° C. by means of a heating bath during the course of themethod. While stirring, the pH of the solution was adjusted to 8.3 with3.39 parts of 10% sodium hydroxide. Total organic solids in the solutionwas 22.2%. The reaction was maintained at pH 8.3. Progress of thereaction was monitored by means of a #3 Shell cup. When viscosity hasadvanced to 8 seconds, second charge to the vessel was made. This chargewas comprised of 9.18 parts of 44% component B, 3.31 parts of 40%glyoxal, and 10.83 parts of water. The pH was adjusted to 8.3 with 0.53parts of 10% sodium hydroxide. Temperature was also maintained at 30° C.After addition of the second charge, the ratio between components A andB on a real weight basis was 80 to 20 and total organic solids in thesolution was 22.2%. When a viscosity of 22 seconds was achieved, the pHwas decreased to 7.9 with 10% sulfuric acid. When a viscosity of 27seconds was achieved, the reaction was quenched by adjusting the pH ofthe polymer solution to 3.3. Total reaction time was 3 hr 25 min. Theresults are shown in Table 5 below.

TABLE 5 Tensile Tensile Tensile Strength Strength Strength 30 MinuteDose Dry Wet Soak Resin (kg/ton) (kN/m) (kN/m) (kN/m) % Decay Example 115 2.97 0.39 0.12 68.92 Example 12 5 2.81 0.34 0.10 69.11 U.S. Pat. No. 53.07 0.40 0.14 64.63 4,605,702 Comparative

These experiments show the effect of glyoxalation of the second backboneat high solids. In both cases, acceptable wet tensile decay wasobtained. The dry tensile development, however, was poorer than thecontrol.

Although the present invention has been described in detail withreference to certain preferred versions thereof, other variations arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the versions contained therein.

1. A method for making a thermosetting resin comprising: (a) treating afirst polyacrylamide backbone with a first glyoxal component,glyoxalating the first polyacrylamide backbone, and thereby forming afirst partially crosslinked polyacrylamide backbone; (b) adding a secondpolyacrylamide backbone and a second glyoxal component to the firstpartially crosslinked backbone, thereby glyoxalating the first partiallycrosslinked polyacrylamide backbone and the second crosslinkedpolyacrylamide backbone in situ and forming the thermosetting resin;wherein the first polyacrylamide backbone has a lower molecular weightthan the molecular weight of the second polyacrylamide backbone; andwherein the first polyacrylamide backbone and the second polyacrylamidebackbone have a weight ratio ranging from 75:25 to 95:5.
 2. The methodof claim 1, wherein the method further comprises glyoxalating the firstpolyacrylamide backbone and the second polyacrylamide backbonesimultaneously with the first glyoxal component and the second glyoxalcomponent, and thereby forming the thermosetting resin.
 3. The method ofclaim 1, wherein the first partially crosslinked backbone solution has a#3 Shell Cup viscosity of 9 seconds.
 4. The method of claim 2, whereinthe simultaneous glyoxalation of the first polyacrylamide backbone andthe second polyacrylamide backbone continues until the solution has a #3Shell Cup viscosity of 27 seconds.
 5. The method of claim 1, wherein thefirst partially crosslinked backbone solution has a solids contentranging from 17 to 22%.
 6. The method of claim 1, wherein the firstpartially crosslinked backbone solution has a solids content rangingfrom 18 to 20%.
 7. The method of claim 1, wherein the glyoxalation pH ofthe first and second stages in steps (a) and (b) ranges from 7 to
 9. 8.The method of claim 1, wherein the method is carried out at atemperature ranging from 15 to 35° C.
 9. The method of claim 1, whereinthe resin is nonionic or ionic and the (i) first partially crosslinkedglyoxalated polyacrylamide backbone or (ii) the second polyacrylamidebackbone further comprises a non-ionic or anionic component selectedfrom the group consisting of acrylamide, acrylic acid, methacrylic acid,succinic acid, itaconic acid, methacrylamide.
 10. The method of claim 1,wherein the first polyacrylamide backbone is selected from the groupconsisting of (meth)acrylamide, vinyl acetate, styrene, methyl(meth)acrylate, (meth)acrylic acid, vinyl alcohol,diallyldimethylammonium chloride, diallyldimethylammonium sulfate, vinylpyrrolidone, (meth)acrylonitrile, dimethylaminoethyl (meth)acrylate,dimethylaminoethyl (meth)acrylate quaternaries, diethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate quarternaries,N-methylol acrylamide, manniched acrylamide quaternaries, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate,(meth)acrylamidopropyltrimethylammonium chloride, succinic acid,itaconic acid, maleic acid, alkylcarboxyvinyl amine.
 11. The method ofclaim 1, wherein the second polyacrylamide backbone is selected from thegroup consisting of (meth)acrylamide, vinyl acetate, styrene, methyl(meth)acrylate, (meth)acrylic acid, vinyl alcohol,diallyldimethylammonium chloride, diallyldimethylammonium sulfate, vinylpyrrolidone, (meth)acrylonitrile, dimethylaminoethyl (meth)acrylate,dimethylaminoethyl (meth)acrylate quaternaries, diethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate quarternaries,N-methylol acrylamide, manniched acrylamide quaternaries, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate,(meth)acrylamidopropyltrimethylammonium chloride, succinic acid,itaconic acid, maleic acid, alkylcarboxyvinyl amine.